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The goal of green chemistry is to reduce or eliminate the use and generation of chemicals that are hazardous to humans, animals, plants and the environment. More specifically, its aim is to promote resource-efficient and inherently safer molecules, materials, products, and processes.

The field came into being in 1991 as a response to the U.S. Pollution Prevention Act, which called on the U.S. to eliminate pollution through improved design instead of through treatment and disposal of waste. Paul Anastas, an organic chemist working for the U.S. Environmental Protection Agency, and John C. Warner developed the 12Ìýguiding principles of green chemistry. They range from the use of safer solvents, and renewable raw materials to the development of energy-efficient processes and chemicals that can degrade and be discarded easily.

12ÌýPrinciples of Green Chemistry

1. Prevention
   It is better to prevent waste than to treat or clean up waste after it has been created.
2. Atom Economy
   Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.
3. Less Hazardous Chemical Syntheses
   Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
4. Designing Safer Chemicals
   Chemical products should be designed to effect their desired function while minimizing their toxicity.
5. Safer Solvents and Auxiliaries
   The use of auxiliary substances (e.g., solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used.
6. Design for Energy Efficiency
   Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, synthetic methods should be conducted at ambient temperature and pressure.
7. Use of Renewable Feedstocks
   A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable.
8. Reduce Derivatives
   Unnecessary derivatization (use of blocking groups, protection/ deprotection, temporary modification of physical/chemical processes) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste.
9. Catalysis
   Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
10. Design for Degradation
    Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment.
11. Real-time analysis for Pollution Prevention
    Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.
12. Inherently Safer Chemistry for Accident Prevention
    Substances and the form of a substance used in a chemical process should be chosen to minimize the potential for chemical accidents, including releases, explosions, and fires.

Anastas, P. T. and Warner, J. C. Green Chemistry: Theory and Practice. Oxford University Press: New York, 1998, p. 30. By permission of Oxford University Press.

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